1. Field of the Invention
This invention relates to optical code readers. In particular, this invention relates to a system and method for aiming an optical code scanning device at a selected optical code.
2. Description of the Prior Art
Optical code scanner systems have been developed heretofore for reading optical codes such as bar code symbols appearing on a label or on a surface of an article. The symbol itself is a coded pattern of indicia comprised of, for example, a series of bars of various widths spaced apart from one another to bound spaces of various widths, where the bars and spaces having different light reflecting characteristics. The scanning devices in scanning systems electro-optically transform the graphic indicia into electrical signals, which are decoded into alphanumeric characters that are intended to be descriptive of the article or some characteristic thereof. Such characters are typically represented in digital form and utilized as an input to a data processing system for applications in point-of-sale processing, inventory control and the like.
Optical code scanning devices are used in both fixed and portable installations in many diverse environments, such as in stores for check-out services, in manufacturing locations for work flow and inventory control, and in transport vehicles for tracking package handling. The scanning device can be used for rapid data entry, such as by scanning a target barcode from a printed listing of many barcodes. In some uses, the optical code scanning device is connected to a portable data processing device or a data collection and transmission device. Frequently, the optical code scanning device is a handheld scanning device including a handheld sensor which is manually directed at a target code.
Often an individual scanning device is a component of a much larger system including other scanning devices, computers, cabling, data terminals, etc. Such systems are frequently designed and constructed on the basis of mechanical and optical specifications for the scanning engine, sometimes called “form factors”. One such form factor is the SE1200 form factor designed by Symbol Technologies, Inc.
One type of optical code scanning device is an array optical imager scanning device, which includes an image sensor having a one- or two-dimensional array of cells or photo sensors, such as an area charge coupled device (CCD). The imager scanning device images a target, including sensing light reflected off a target being imaged and generating a plurality of electrical signals corresponding to the sensing which correspond to a two-dimensional array of pixel information describing the field of view of the scanning device. The electrical signals are then processed and provided to decode circuitry for decoding thereof. The imager sensor includes associated circuitry for generating and processing the electrical signals. In addition, a lens assembly may be provided for focusing light incident on the image sensor.
When multiple optical codes are in the field of view (FOV) of the scanning device, the scanning device typically determines which optical code is the easiest to capture and/or read, and that optical code is decoded first. The user does not control which optical code the system should try to decode, and accordingly may have difficulty scanning a desired optical code.
Scanning devices are often equipped with an aiming assembly which generates a visible aiming pattern, such as a “cross hair” pattern, which a user may train on a target object to be imaged in order to aim the scanning device at the target image. In commercially available imaging devices it is common for the center of the aiming pattern to not coincide with the center of the field of view of the scanning device due to mechanical or manufacturing inconsistencies, including the displacement between a light source of the aiming assembly and a focal point of optics for focusing light onto the image sensor. The user may use the aiming pattern to scan a desired code that is presented together with multiple optical codes, such as on a page having one or more columns of optical codes. The user may try to align the center of the aiming pattern to coincide with or be nearest to the desired code and then activate a scanning operation, such as by pulling a trigger.
Upon activation of the scanning operation, the scanning device temporarily disables generation of the aiming pattern so that the aiming pattern is not incorporated into the image being acquired in order not to obstruct a target being imaged. The actual position of the aiming pattern in the acquired image is not necessarily in the center of the acquired image. In fact, the actual position of the aiming pattern is not known. The desired optical code is not necessarily the acquired optical code that is closest to the center of the acquired image. Accordingly, there is not a reliable way to determine which optical code of the multiple optical codes lying within the field of view of the scanning device is the desired optical code.
Accordingly, there is a need for a system and method for aiming an optical code scanning device at a desired optical code of multiple optical codes in the field of view of the scanning device for decoding the desired optical code.